The present system relates generally to empty load devices and more specifically to a lock-out mechanism for an empty load device.
An empty load device is a device connected between the brake control valve and the brake cylinder. It senses the load in the car and determines how much of the brake signal from the control valve is to be provided to brake cylinder. If the device is loaded, a full signal is provided. If the device is not loaded, then a percentage of the brake signal is provided to the brake cylinder. The empty load device has a load sensing element which senses the load of the car and controls a changeover valve. The changeover valve is retained fully opened and connects the inlet with the outlet when the car is loaded and closes when the car is empty. The changeover valve also includes a pressure differential element which determines the proportioning of the brake signal to the brake cylinder when the changeover valve is changed over (closed) into the empty load position.
Although the changeover valves have historically been developed to either be empty or loaded, there are valves that have been designed which will adjust to different degrees of loading.
A typical empty load valve is disclosed in U.S. Pat. No. 5,211,450 to Gayfer et al., in a single housing. Another patent to Gayfer et al., U.S. Pat. No. 6,666,528, shows the load sensing and the proportion valve being in two different housing. Both these patents are incorporated herein by reference. In each of these, an arm is used to sense the displacement between the car body and the truck as an indication of weight. For bulk commodity cars, where access to the load sensing is through the wall of the bin. This type of empty load device may be used as exemplified by the Bacon U.S. Pat. No. 3,960,411. A device disclosed by Beacon et al., U.S. Pat. No. 5,039,174, shows the same structure used for bulk commodity cars as well as those which measure the load by the displacement between the truck and the body.
For certain tests and adjustments of the brake system, it is important that the empty load device be disabled such that it does not go into the empty load car condition. Pasek, U.S. Pat. No. 5,417,143, provides a lock-out mechanism for the empty/load to changeover valve. This is a mechanical lock-out of the actuator rod of the load sensing portion. Lock-out mechanism is automatically reset upon retraction of the actual rod.
The present empty/load device includes an inlet to receive a brake signal, an outlet for a brake device, load sensing element, a change over valve responsive to the load sensing element to proportion the pressure at the inlet and the outlet when empty is sensed by the load sensing element, a differential pressure element connecting the load sensing element and the change over valve, and a lock-out mechanism to prevent proportioning of the inlet pressure to the outlet when activated. The lock-out mechanism includes a lock-out valve, in a lock-out position, pneumatically preventing proportioning of the inlet pressure to the outlet. A first spring biases the lock-out valve from the lock-out position. A detent engages the lock-out valve and holds the lock-out valve in the lock-out position.
The lock-out valve may be connected in parallel to the change over valve with respect to the inlet and the outlet. Alternatively, the lock-out valve may be connected in parallel to the both sides of the differential pressure element.
The lock-out valve includes a recess for receiving the detent when the lock-out valve is in the lock-out position. A second spring biases the detent into engagement with the lock-out valve. The lock-out valve includes a handle for positioning the lock-out valve to the lock-out position and the detent includes a handle to disengage the detent from the lock-out valve and release the lock-out valve from the lock-out position.
These and other aspects of the present device will become apparent from the following detailed description of the invention, when considered in conjunction with accompanying drawings.